For example, in an audio/video synchronization processing apparatus (AV recording apparatus) such as an input device of an MPEG encoder, generally the frame lengths (frame periods) of input signals of the video data and the audio data are different. Further, it is characterized in the point that the audio data and the video data are fetched in periods of frame units. Below, an explanation will be given of the configuration and mode of operation of such a conventional AV recording apparatus.
FIG. 15 is a view of the system configuration of a conventional AV recording apparatus.
This system is configured by a data controller 2a and a system encoder 3a receiving control commands from a host (HOST) 1a. 
The data controller 2a receives control commands from the host 1a at its audio/video controller (AV_CTRL) 21a and controls an audio controller 22a and a video controller 26a based on time information from a timer (TIMER) 24a. 
Note that, hereinafter, the audio/video controller will be referred to as an “AV controller”.
The AV controller 21a issues control commands to the audio controller (A_CTRL) 22a so as to control the input of the audio data (A_DATA). The input audio data is stored in an audio data memory (A_HEM) 23a. 
Further, the AV controller 21a issues control commands to the video controller (V_CTRL) 26a so as to control the input of the video data (V_DATA). The input video data is stored in a video data memory (V_MEM) 25a. 
The data controller 2a provides the audio data (A_PTS) and the video data (V_PTS) given a PTS (presentation time stamp) as time information to the system encoder 3a based on the time information from the timer 24a. 
The system encoder 3a is controlled by the control commands from the host 1a. The audio encoder (A_ENC) 31a encodes the audio data given the PTS from the data controller 2a. The video encoder (V_ENC) 33a encodes the video data given the PTS from the data controller 2a. A multiplexer (MPX) 32a multiplexes the data encoded by the audio encoder 31a and the video means 33a to generate a bit stream (BSD).
However, in an AV recording apparatus including an MPEG encoder, due to hardware restrictions, the frame periods of the video data and the audio data often cannot be changed. In such cases, if pausing based on the frames of the video data, when subsequently releasing the pause, there is a problem that the audio data will become offset in synchronization from the video data (AV synchronization offset).
With respect to this problem, unless suitable processing is performed, the synchronization offset will build up and the viewer will get a strange feeling.
Below, this conventional problem will be specifically explained by using FIG. 16.
FIG. 16 is a diagram showing an example of the AV synchronization offset when controlling the pause and pause release.
In the conventional AV recording apparatus shown in FIG. 15, the control for fetching the data can only be carried out in frame units. Further, the frame periods of the video data and the audio data (video_frame_time and audio_frame_time) cannot be changed even during a pause.
In FIG. 16, when receiving a pause request (indicated as “P” in the figure) from the host 1a, the pause request is reflected in the data controller 2a at the time t161 of a break between frames in the video data 1. The audio data exists in the middle of the frame period at the time t161, and the pause request is reflected in the next audio frame, therefore tp161 is generated as a difference of the video data and the audio data at the time of a pause.
During a pause, the frame period of the video data and the frame period of the audio data remain unchanged. The difference tp161 between the video data and the audio data at the time of the pause remains as generated uncorrected.
When receiving a pause release request (indicated as “P_RL” in the figure) from the CPU 1a, the pause release request is reflected in the data controller 2a at the timing of the time t162 of the start of input of the video data n (VDn). Here, at the time of pause release, when adjusting the timing of the audio data with respect to the video data by considering the difference tp161 between the video data and the audio data at the time of the pause, no AV synchronization offset occurs.
However, since the difference of frame periods of the video data and the audio data causes generation of the difference tp162 from the time t162 of the pause release to the time of start of input of the audio input data n (ADn) as the difference between the audio data and the video data at the time of pause release, the result is that an AV synchronization offset tp163 occurs at the time of pause release from the time t161 and time tp162.
Particularly, when the frame periods of the video data and the audio data cannot be changed, this tp163 may accumulate with each pause request, therefore will sometimes be perceived as strange.